Method and device for regulating a docking process between two automobiles

ABSTRACT

A method is for regulating the speed of an automobile and the distance of the automobile from at least one automobile driving in front during a docking process, the driving speed of the automobile being greater than that of the automobile in front. According to the method, a detection device with a distance sensor is used to determine at least the speed of the automobile, the relative speed and the distance from the automobile in front, and the value of a normal acceleration for a braking operation of the vehicle is calculated according to the difference between a predetermined normal desired following distance and the distance and the relative speed. The technical problem of further improving the functioning of a method of this type and the corresponding device and ensuring comfortable driving behavior during the docking process between the two automobiles is solved by calculating the value for a limit acceleration for a braking operation of the automobile according to the difference between a predetermined limit desired following distance and the distance and the relative speed, by determining the greater of the two values for the normal acceleration and the limit acceleration in terms of amount, as the braking acceleration to be applied, and braking the automobile with the braking acceleration. A device for performing the method includes two proportionality regulators for calculating the normal acceleration and the limit acceleration.

[0001] The present invention relates to a method and a device for regulating the speed of a motor vehicle and the distance of a motor vehicle from at least one motor vehicle driving ahead during a docking operation, the motor vehicle having a greater driving speed than the preceding motor vehicle.

[0002] It is known from the methods for automatic ranging (ADR) known from the related art that at least speed v of the vehicle, relative velocity V_(rel) and distance s_(actual) from the preceding vehicle are determined with the help of a detection device having a distance sensor. Moreover, the value of a normal acceleration a_(n) is calculated for braking of the vehicle as a function of the difference between a predefined standard setpoint trailing distance s_(n) and distance s_(actual) and of relative velocity V_(rel). The vehicle is then braked at the normal acceleration, which is negative for a deceleration, in order to regulate the vehicle to standard setpoint trailing distance s_(n).

[0003] However, if the relative velocity of the two vehicles is too high, the braking effect exerted by the automatic ranging system is not sufficient to prevent the an insufficient setpoint trailing distance, i.e. the safety distance, or even a rear-end collision. The driver is then forced to actively intervene and trigger a greater braking effect. This problem arises particularly when the controlled variables for the automatic ranging system are set to a relatively large standard setpoint trailing distance s_(n) and to low values for reliable normal accelerations a_(n).

[0004] Such a method is known from the related art of EP 0 846 587 A1, in which the distances to an object detected in front of the motor vehicle is detected by a distance sensor and is supplied to a control device, which forms one or more controlled variables at least as a function of a setpoint distance from a detected object determined at least from the instantaneous driving speed and/or of a predefined setpoint speed to adjust the driving speed of the motor vehicle.

[0005] Furthermore, a control device for maintaining a safety distance for a motor vehicle is known from U.S. Pat No. 5,165,497 that sets the safety distance between the motor vehicle and the preceding motor vehicle in a speed range of 0 to 120 km/h in order to prevent a collision. The control performed by the control device goes so far that when the preceding vehicle stops, the vehicle is decelerated to a standstill. If the preceding vehicle then starts again, the vehicle also starts again. Consequently, there is a coupling between the vehicles, significant acceleration changes resulting in less comfortable handling properties being able to occur.

[0006] Starting out from this related art, the present invention is based on the technical problem of further improving the functioning method of the method of this type as well as of the corresponding device and facilitating more operator-friendly handling properties during the docking operation between two motor vehicles.

[0007] The previously indicated technical objective is first achieved by a method according to claim 1 in that the value of a limiting acceleration a_(g) is calculated for a deceleration of the vehicle as a function of the difference between a predefined setpoint limiting trailing distance s_(g) and distance s_(actual) and relative velocity V_(rel), in that the value of the two values of normal acceleration a_(n) and of limiting acceleration a_(g) having the greater magnitude is determined as braking acceleration a_(b) to be used, and in that the vehicle is decelerated using a braking acceleration a_(b). In this context, limiting acceleration a_(g) and setpoint limiting trailing distance s_(g) represent parameters that for automatic ranging are at a setpoint trailing distance at the bottom limit or at an acceleration values to be used at the top limit for automatic ranging. The smallest setpoint trailing distance or safety distance corresponds to a trailing time of about 0.9 seconds, i.e., at every speed, the vehicle is to follow the preceding vehicle at a time interval of at least 0.9 seconds. However, the terms normal acceleration a_(n) and standard setpoint trailing distance s_(n) represent parameters deviating from the previously discussed limiting values and corresponding to an automatic ranging system having a greater safety distance and lower maximum acceleration values.

[0008] In accordance with the present invention, it was recognized that the above described problematic driving situation in which the relative velocity of the two motor vehicles is not sufficient for the set “normal” automatic ranging is able to be at least partially detected in that limiting acceleration a_(g) is calculated in parallel with normal acceleration a_(n) and in that limiting acceleration a_(g) is used when a deceleration of the motor vehicle at normal acceleration a_(n) is not sufficient for docking the vehicle. In this context, the driver of the motor vehicle is not prevented in every case from intervening. However, more significant braking than for normal automatic distance ranging increases the range of driving situations that are able to be controlled by the automatic distance ranging system in a comfortable manner without the intervention of the driver.

[0009] In a preferred manner, the magnitude of normal acceleration a_(n) and/or of limiting acceleration a_(g) increases as relative velocity V_(rel) increases or as distance s_(actual) decreases. This means that when relative velocity V_(rel) is large, the automatic ranging system generates greater acceleration values than is the case for smaller values of relative velocity V_(rel). The same is true for the situation in which distance s_(actual) between both motor vehicles is small. If in this context the value of limiting acceleration a_(g) increases more significantly than the value of normal acceleration a_(n), the method of the present invention begins at or above the parameters relative velocity V_(rel) and distance s_(actual) as limiting acceleration a_(g) is greater than normal acceleration a_(n).

[0010] In a further preferred manner, normal acceleration a_(n) is calculated with the help of a proportionality controller using a characteristics map using two input variables, namely relative velocity V_(rel) and the difference between standard setpoint trailing distance s_(n) and actual distance s_(actual). It is also preferred that limiting acceleration a_(g) is calculated with the help of a proportionality controller using a characteristics map using two input variables, namely relative velocity V_(rel) and the difference between setpoint limiting trailing distance s_(g) and actual distance s_(actual). A more precise mathematical description of an exemplary embodiment is explained in the following on the basis of the description of the drawing.

[0011] It is also preferred that standard setpoint trailing distance s_(n) is calculated from speed v of the motor vehicle and a predefined standard trailing time t_(n). Setpoint limiting trailing distance s_(g) may also be calculated from speed v of the motor vehicle and a predefined limiting trailing time t_(g). According to experience, limiting trailing time t_(g) already mentioned above has a value of about 0.9 seconds. In comparison, typical values for standard trailing time t_(n) are in the range of 0.9 to 4.0 seconds, in particular up to 2.0 seconds. Since an adjustment of the trailing time by the driver is intuitive, this refinement of the adjustment of the trailing distance is often used with the help of a trailing time.

[0012] Finally, it is preferred that the time characteristic of braking acceleration a_(b) of the motor vehicle is constant during the transition between normal acceleration a_(n) and limiting acceleration a_(g), i.e., there is no abrupt change between the two acceleration values. This further increases the comfort of the automatic ranging system since there is no jolt in the movement of the vehicle.

[0013] The above indicated technical objective is achieved in accordance with the present invention by a device according to the features of claim 13. This device is explained below in detail, using an exemplary embodiment, reference being made to the enclosed drawing. In this drawing, the figures show:

[0014]FIG. 1 shows a block diagram of an exemplary embodiment of a device of the present invention; and

[0015]FIG. 2 shows a graphic representation of the functional characteristics of normal acceleration a_(n) and of limiting acceleration a_(g) for two different distances s_(actual)(1) and s_(actual)(2) between the two motor vehicles.

[0016]FIG. 1 shows a device of the present for implementing a method for regulating the speed of a motor vehicle and the distance of the motor vehicle from at least one motor vehicle driving ahead during a docking operation, the motor vehicle having a greater speed v than the preceding motor vehicle. The device has a detection device not shown in FIG. 1 having at least one distance sensor for determining at least speed v of the motor vehicle, relative velocity V_(rel), and distance s_(actual) from the preceding vehicle. The device also has an evaluation unit that is partially shown in FIG. 1. In addition, FIG. 1 shows a first proportionality controller 2, which uses a characteristics map to calculate a normal acceleration a_(n) using two input variables. The two input variables are relative velocity V_(rel) and the difference between standard setpoint trailing distance s_(n) and actual distance s_(actual). The proportionality controller uses the two input variables to calculate the corresponding value of normal acceleration a_(n) and outputs it.

[0017] The evaluation unit shown in FIG. 1 also has a second proportionality controller 4 having a characteristics map for calculating a limiting acceleration a_(g) that also uses two input variables. They are relative velocity V_(rel) and the difference between setpoint limiting trailing distance s_(g) and actual distance s_(actual). With the help of these two input variables, proportionality controller 4 calculates the corresponding value of limiting acceleration a_(g) and outputs it as an output variable.

[0018] Furthermore, the evaluation unit has a comparing element 6 for determining the value of the two values of normal acceleration a_(n) and limiting acceleration a_(g) having a greater magnitude, the greater of the two values being output as an output variable as braking acceleration a_(b). This value is then assumed by the engine and brake management in order to deceleration the vehicle.

[0019] Typical electronic differential elements 8 and 10 are provided for forming the differences between standard setpoint trailing distance s_(n) and setpoint limiting trailing distance s_(g), respectively, and actual distance s_(actual).

[0020] On the basis of in each case two functional characteristics, FIG. 2 shows normal acceleration a_(n) and limiting acceleration a_(g) for two different actual distances s_(actual)(1) and s_(actual)(2).

[0021] Both functions are linear functions that are calculated in accordance with the formula for normal acceleration a_(n) using $a_{n} = {{a_{n,0} + {{a_{n,1} \cdot \frac{v_{rel}}{s_{n} - s_{ist}}}\quad {for}\quad s_{n}} - s_{ist}} > {\Delta \quad s_{0}}}$

 and

a _(n) =a _(n,max) for s _(n) −s _(ist) ≦Δs ₀.

[0022] as well as for limiting acceleration a_(g) using $a_{g} = {{a_{g,0} + {{a_{n,1} \cdot \frac{v_{rel}}{s_{g} - s_{ist}}}\quad {for}\quad s_{g}} - s_{ist}} > {\Delta \quad s_{1}}}$

 and

a _(g) =a _(g,max) for s _(g) −s _(ist) ≦Δs ₁.

[0023] Therefore, they are essentially linear functional characteristics having different offsets a_(n,0) and a_(g,0) as well as linear slopes a_(n,1) and a_(g,1). The use of the values Δs₀ and Δs₁ for purposes of differentiating results in a maximum value being used in each case for normal acceleration a_(n) and limiting acceleration a_(g) when the difference between standard setpoint trailing distance s_(n) or setpoint limiting trailing distance s_(g) and actual distance s_(actual) tends to zero. This limiting-value characteristic is not shown in the graphic representation in FIG. 2.

[0024] It also becomes clear from the formulas that the values of normal acceleration a_(n) and limiting acceleration a_(g) increase as relative velocity V_(rel) increases and the distance decreases for values above standard setpoint following distance s_(n) or setpoint limiting trailing distance s_(g). It is emphasized that the indicated formulas are only an exemplary embodiment representing the relationships between the parameters. Of course, other functional characteristics, in particular non-linear functions, may be used.

[0025] Both proportionality controllers 2 and 4 use characteristic maps that each use two input variables as described above. The characteristic maps are made up of a plurality of curves that are exemplarily and sectionally shown for two different distances s_(actual) in FIG. 2 and are consequently characterized. If one first considers for a first distance s_(actual)(1) the characteristic of the two values for normal acceleration a_(n) and limiting acceleration a_(g) as a function of relative velocity V_(rel), both lines intersect at a point that is characterized in the coordinate system in FIG. 2 by dotted lines. If relative velocity V_(rel) is less than the value of the relative velocity for the intersection, the value of normal acceleration a_(n) is used as the greater of the two acceleration values. Limiting acceleration a_(g) is used for relative velocities V_(rel) above the value of the relative velocity characterizing the intersection.

[0026] In comparison, the two lines for the values of accelerations a_(n) and a_(g) are shown for a second distance s_(actual)(2) that is less than distance s_(actual)(1). Since the distance between the two motor vehicles in this situation is smaller, a greater braking effect must be attained in total in order to prevent setpoint limiting trailing distance s_(g) from not being met. Therefore, the dotted lines are above the solid lines in FIG. 2. The intersection between the two dotted lines is present at lower relative speeds as well as at a greater value for acceleration a. Consequently, limiting acceleration a_(g) is rather used for smaller distance s_(actual)(2) than is the case for first greater distance s_(actual)(1). Therefore, the result is that the motor vehicle is more significantly decelerated in the case of smaller distance s_(actual)(2) than in the case of greater distance s_(actual)(1). 

What is claimed is:
 1. A method for regulating the speed of a motor vehicle and the distance of the motor vehicle from at least one vehicle driving ahead during a docking operation, the motor vehicle having a greater driving speed (v) than the preceding motor vehicle, in which at least the speed (v) of the vehicle, the relative velocity (V_(rel)), and the distance (s_(actual)) from the preceding vehicle are determined using a detection device having a distance sensor; and in which the value of a normal acceleration (a_(n)) is calculated for a deceleration of the motor vehicle as a function of the difference between a predefined standard setpoint trailing distance (s_(n)) and the distance (s_(actual)) and the relative speed (V_(rel)), wherein the value of a limiting acceleration (a_(g)) is determined for a deceleration of the motor vehicle as a function of the difference between a predefined setpoint limiting trailing distance (s_(g)) and the distance (s_(actual)) and the relative velocity (V_(rel)); the value of the two values of the normal acceleration (a_(n)) and the limiting acceleration (a_(g)) having the greater magnitude is determined as the braking acceleration (a_(b)) to be used; and the motor vehicle is decelerated at the braking acceleration (a_(b)).
 2. The method as recited in claim 1, wherein the magnitude of the normal acceleration (a_(n)) and/or of the limiting acceleration (a_(g)) increases as the relative velocity (V_(rel)) increases.
 3. The method as recited in claim 1 or 2, wherein the magnitude of the normal acceleration (a_(n)) and/or of the limiting acceleration (a_(g)) increases as the distance (s_(actual)) decreases.
 4. The method as recited in one of claims 1 through 3, wherein the normal acceleration (a_(n)) is calculated with the help of a proportionality controller using a characteristics map using two input variables (V_(rel), s_(n)−s_(actual)).
 5. The method as recited in claim 4, wherein the value of the normal acceleration (a_(n)) is calculated as $a_{n} = {{a_{n,0} + {{a_{n,1} \cdot \frac{v_{rel}}{s_{n} - s_{ist}}}\quad {for}\quad s_{n}} - s_{ist}} > {\Delta \quad s_{0}}}$

and a _(n) =a _(n,max) for s _(n) −s _(ist) ≦Δs ₀.
 6. The method as recited in one of claims 1 through 5, wherein the limiting acceleration (a_(g)) is calculated with the help of a proportionality controller using a characteristics map using two input variables (V_(rel), S_(g)−s_(actual)).
 7. The method as recited in claim 6, wherein the value of the limiting acceleration (a_(g)) is calculated as $a_{g} = {{a_{g,0} + {{a_{n,1} \cdot \frac{v_{rel}}{s_{g} - s_{ist}}}\quad {for}\quad s_{g}} - s_{ist}} > {\Delta \quad s_{1}}}$

and a _(g) =a _(g,max) for s _(g) −s _(ist) ≦Δs ₁
 8. The method as recited in claims 5 and 7, wherein a_(n,0) is set to be greater than a_(g,0).
 9. The method as recited in claims 5 and 7, wherein a_(n,1) is set to be less than a_(g,1).
 10. The method as recited in one of claims 1 through 9, wherein the standard setpoint trailing distance (s_(n)) is calculated from the speed (v) of the motor vehicle and a predefined standard trailing time (t_(n)).
 11. The method as recited in one of claims 1 through 10, wherein the setpoint limiting trailing distance (s_(g)) is calculated from the speed (v) of the motor vehicle and a predefined limiting trailing time (t_(g)).
 12. The method.as recited in one of claims 1 through 11, wherein the time characteristic of the braking acceleration (a_(b)) of the motor vehicle is constant during the transition between the normal acceleration (a_(n)) and the limiting acceleration (a_(g)).
 13. A device for implementing a method for regulating the speed of a motor vehicle and the distance of the motor vehicle from at least one vehicle driving ahead during a docking operation, the motor vehicle having a greater driving speed (v) than the preceding vehicle, having a detection device having at least one distance sensor for determining at least the speed (v) of the motor vehicle, the relative velocity (V_(rel)), and the distance (s_(actual)) from the preceding motor vehicle; having an evaluation unit including a first proportionality controller (2) including a characteristics map for calculating a normal acceleration (a_(n)) using two input variables (V_(rel), S_(n)−s_(actual)), wherein the evaluation unit has a second proportionality controller (4) including a characteristics map for calculating a limiting acceleration (a_(g)) using two input variables (V_(rel), S_(g)−s_(actual)); and the evaluation unit has a comparing element (6) for determining the value of the two values of the normal acceleration (a_(n)) and the limiting acceleration (a_(g)) having the greater magnitude.
 14. The device as recited in claim 13, wherein the evaluation unit outputs the greater of the two values of the normal acceleration (a_(n)) and the limiting acceleration (a_(g)) as the value of the braking acceleration (a_(b)). 